QUANTUM CHEMICAL STUDY OF ZrO_2 ATOMIC LAYER DEPOSITION ON THE SiO_2 SURFACE

摘要

Zirconium oxide (ZrO_2) deposited on silicon has the potential of replacing silicon oxide (SiO_2) as the gate dielectric for metal-oxide-semiconductor (MOS) transistors. This study uses Density Functional Theory (DFT) to investigate the initial growth of ZrO_2 on SiO_2 by atomic layer deposition (ALD). The reactants investigated in this study are zirconium tetrachloride (ZrCl_4) and water (H_2O). Exchange reaction mechanisms for the two reaction half-cycles were investigated. For the first half-reaction, reaction of gaseous ZrCl_4 with the hydroxylated SiO_2 surface was studied. Upon adsorption, ZrCl_4 forms a stable intermediate complex with the surface SiO_2-OH* site, followed by formation of SiO_2-O-Zr-Cl* surface sites and HCl. For the second half-reaction, reaction of H_2.O on SiO_2-O-Zr-Cl* surface sites was investigated. The reaction pathway is analogous to that of the first half-reaction; water first forms a stable intermediate complex followed by evolution of HCl through combination of a Cl from the surface site and an H from H_2O. The results reveal thai the stable intermediate complexes formed in both half-reactions trap the reaction unless process parameters are adjusted to lower the stability of the complex. The energetics of the two half reactions are similar to those of ZrO_2 ALD on ZrO_2 as well as the energetics of ZrO_2 ALD on hydroxylated silicon.